For many types of truck container shipments, it is required or desirable to cover the open top of the container to retain the cargo therein during transportation. Waste and other loose materials subject to spilling during hauling are particularly in need of such preventive measures. Inasmuch as the size of such containers vary widely, it is important that the covering apparatus accommodate the expected height, width and volumetric conditions without the need for customized apparatus.
A number of approaches in the art have sought to provide a spooled cover sheet that could be extended over the length of the load. Oftentimes, however, such apparatus, is not able to handle significant variations in length without structural modification. Such problems, to a large extent are overcome by the truck container covers as disclosed in U.S. Pat. Re. No. 36,135, issued in the name of the inventor of the present application. Therein, a pair of articulated arms is supported on either side of the container. Each arm has a base arm pivotally connected at a lower end to a base positioned midway along the container. A hydraulic cylinder spans the lower pivotal connection and is effective to pivot the base arm between a forward stowed position and a rearward covered position. An extension arm is pivotally connected to the upper end of the base arm. A second hydraulic cylinder spans the upper pivotal connection. The upper ends of the extension arms are operatively connected to a rolled cover. By selectively actuating the cylinders, the arms can upwardly pivot over containers of various heights, and during rearward pivotal movement may be closely positioned with respect to the open top of the container. Such a system provides flexibility in handling a wide variety of containers.
Nonetheless, certain problems can arise during normal loading and unloading of the container onto the vehicle. Vehicles such a wastehaulers are equipped to interchangeably handle a plurality of containers of varying sizes. Such containers are generally forwardly shifted upwardly along a tilted frame and thereafter pivoted to the horizontal position. During such positioning, unless accurately aligned, the container may impact various components of the cover system. The hydraulic cylinders are vertically and horizontally exposed and may be impacted, damaged and misaligned during normal container transfer. Moreover, the extension arms are particularly prone to damage during normal usage. The resulting damage oftentimes requires time consuming and costly repairs.
Further, the articulation system requires long stroke cylinders inasmuch as the cylinders are disposed in a second class lever system spanning the pivotal connection. Inasmuch as the lower arm may pivot in excess of 140.degree., the piston stroke to enable such movement is substantial. The actuators are accordingly quite expensive. Further, the lever arm disposition in such a system varies considerably during the allowed movement and is substantially foreshortened toward the end positions. This increases the loading on the pivots and arms during rolling and unrolling of the cover. Thus in addition to the piston stroke length, the actuator capacity must be sufficient to handle the loading without excessive wear and maintenance further increasing component costs. Additionally, the cylinder length and disposition, together with the required spacing between front and rear stop plates for limiting arm rotation, requires substantial base from length, increasing the system size, weight and cost.
In view of the foregoing, it is an object of the present invention to provide a two stage articulated covering system for open top containers resistive to damage during loading and unloading of the container.
Another object of the invention is to provide a compact, low profile two-stage articulated automated cover system for open top containers having a compact, shielded actuator system.
A further object of the invention is to provide an actuating system for selectively pivoting the arms of an articulated automated container covering apparatus, providing smooth, even movement of the arms during covering and uncovering of the container.